Method of treating raw sugar-juices.



A. KRAFFT.

METHOD OF TREATING RAW SUGAR JUICES.

APPLICATION FILED MAR.7,19I7- RENEWED DEF. 1.19M-

1 ,2? 1,9 1 4, Patented July 9, 1918.

E p if 5 TEA/7 BOILERS ALFRED KRAFFT, OF HONOLULU, TERRITORY OF HAWAII.

METHOD OF TREATING RAW SUGAR-JUICES.

Application filed March 7, 1917, SerialNo. 153,018. Renewed December 1,1917.

To all whom it may concern:

Be it known that I, ALFRED KRAFFT, a subject of the King of GreatBritain, res1ding at Honolulu, Territory of Hawail, have inventedcertain new and u eful Improvements in Methods of Treati Raw Sugar-Juices; and I do hereby declare the following to be a full, clear, andexact description of the invention, such as will enableothers skilled inthe art to which it appertains to make and use the same.

This. invention relates to the treatment of sugar juices as the same aredelivered from the crushing rolls, and preferably after the juices havebeen submitted to the usual limin operation, and consists essentially insu jecting the juices to the direct action of hot flue gases, such asare delivered from a steam boiler or other similar furnace, the juicespreferably being" brought into direct and inti ate contact with theproducts of combusti n, in spray-likeform, the action of the flue gasesroducing certain marked advantageous e ects, hereinafter enumerated,which result in material economies in the operation of sugar mills, aswill be more particularly described hereinafter.

The accompanying drawing is a dlagrammatic illustration of a modernsugar mill, involving apparatus for carrying out the present invention.

Referring to the drawings, 1 indicates the usual form of conveyer whichdelivers the cane to the roller mills 2, 2 and 2", which may be of anypreferred form, which mills crush and comminute the cane and extract theraw juices therefrom, which latter are delivered into the usual juicepan 3, whence said juices flow into the usual liming and weighing tank4.

The waste or bagasse fromthe crushing rolls passes by way of the feedchute 5 to the furnaces of a battery of steam boilers 6, which developthe steam necessary for the operation of the plant. The steam boilerfurnaces are connected with the usual stack or chimney 7, which isprovided with a damper or cut-off valve 9. The stack 7 is rovided witha'lateral branch 8 below the amper 9, which, in turn, is provided witha. Similar damper or cut-off 10. The discharge end of the lateral flue 8is connected. with an apparatus designed to bring the flue gases orroducts of combustion from the steam boi er furnaces into direct and'intlmate contact with the sugar juices delivered Specification ofLetters IPetent.

Patented July 9, 1918.

Serial No. 205,002.

from the liming tank 4, said apparatus referably comprislng a verticalcylindrica vessel or container 11 provided with a series of perforatedgrids or grates arranged one above the other throughout the length ofthe container 11, so that the juices delivered to the container by ipe4', provided with a spray head central yl disposed within the upperortion of t e container, will be passed ownward in spray-like formthrough the grids, while the products of combustion are passin upwardthrough said container, the upwar draft being augmented, if necessary,by means of an exhaust fan 15 interposed in the outlet conduit 14 fromthe to of the container and connected to the stac 7, said conduit 14bein provided with a suitable damper or cut-o 16 beyond the fan 15. Thelower portion of the container 11 is provided with a conical baflle 13adjacent the outlet of flue 8, and the lower conical end of saidcontainer is connected with the discharge pipe 17, which is connectedwith the usual settling or decantation tanks 18.

From the upper ortions of said settling tanks, a pipe 19 lea s to theusual battery of quadruple efi'ect evaporators 20, from whence thejuices pass by way of pipe 21 to'vacuum pans 23. From the lower portionsof the settling tanks, a pipe 21 leads to the usual filter presses 26,and from the latter a pipe 27 connects with the pipe 19 leading to theevaporators.

The steam from the boiler 6 is supplied by the usual steam line 10 to anengine 32 for operating the various elements of the mill and also forsupplying the necessary heat to the evaporators 20 and the vacuum pans22, as will be understood.

In carrying out the invention, the damper 9 in the stack 7 is moved toclosed position, and the dampers 10, in flue 8, and 16, in exhaust flue14, are 0 ened, thereby causing the products of com ustion, resultingfrom the burning of the bagasse in the steam, i boiler furnaces, .topass upward through the? bustion from the furnaces directly into thestack, and to employ a portion of the steam enerated in the boilers in aspecial form of uice heater to preliminarily heat the juices delivered,to the heater from the liming tank. This resulted not only in the totalloss of the heat carried by the flue gases but also entailed anadditional element of expense re resented by the steam employed to'heatt e juices in the juice heater to a degree sufficient to effectclarification of the juices in the settling tanks. The presentinvention, however, enables the usual form of juice heaters, constructedlike an ordinary sur-. face condenser, to be entirely dispensed with andsupplanted by the vessel or container 11 in which the juices are broughtinto direct and intimate contact with the products of combustion fromthe steam boiler furnaces. Upon first consideration, it would naturallyoccur to the sugar engineer that the bringing together of the smoky fluegases and the raw sugar juices would prove injurious, if notdestructive, to the juices, but practical demonstration on a commercialscale has proven that the results are directlythe reverse, and evidencesa materially improved condition of the juices for subsequent treatment,as well as marked economy in the operation of the .mill as a whole.

In the waste flue gases from.a bagasse fire,

fine particles of ash and carbonized cane fiber are always present, andit has been found that the latter, especially when mixed directly withthe mill juices,- acts as a decolorizin agent, and also as an absorbentfor the lig ter flocculent matter found in all cane juices andconsisting principally of gums and waxes. This mixing of the solidmatter contained in the flue gases directly with the mill juices,therefore, results in the production of a lighter colored juice fromwhich a higher grade of sugar is obtained than is usually made by theprocesses heretofore in vogue. Another advantage gained by the admixtureof the solid matter contained in the flue gases with the juices is dueto the fact that the solid particles, which are carried along with thejuices discharged from the heater, constitute a filtering medium, withthe result that a materially improved decantation and filtration isobtained in the settling tanks and in the filter presses, andpractically all of the solid and mechanically suspended impuritiescontained in the juices are more readily removed than heretofore.

A still further improvement in the clarification of the mill juice isdirectly predicable upon the chemical action of the juices by thecarbonic acid gas (CO in the flue gases. It is known that over-limingthe raw uices results in a bettersubsequent clarification than can beotherwise obtained, and by utilizing the large quantitiesof carbonicacid in the flue gases as a saturant for the limed juices, any desireddegree of over-liming may be practised with the assurance that theotherwise objectionable condition will be corrected in the heater by theCO present.

One of the most important advantages of the present invention, however,resides in the practical utilization of the heat remaining in theproducts of combustion or flue gases, which heat had heretofore beenpermitted to go to waste. Assumin that bagassee is employed as the fuelfor the steam boiler furnaces, not only is the heat in the products ofcombustion thereof rendered available, but the Water in the form ofsteam in the flue gases also performs a desirable and economicalfunction of heating and evaporating the water content of the juices, sothat the latter are delivered from the heater in materially concentratedform. Bagassee is roughly composed of about 50% moisture, and thebalance of fiber and a small percentage of sugar and non-sugars, and theresulting products of combustion, assuming an air supply to the furnaces100% in excess of that theoretically necessary, will.

be for each pound of bagasse fired, as follows From this tabulation, itwill be seen that there results 5.19 lbs. of flue gases and .79 lbs. ofwater in the form of steam for'every pound of bagasse burned, or a totalof 5.98 lbs. of hot flue gases and steam available not only for heatingthe sugar juices, but for carrying off a material proportion of thewater contained in said juices. It is well known that air and othergases have a capacity for absorbing moisture, which increases with thetemperature of the gases, and as each pound of bagasse burned producesonly .79 lbs. of vapor for each 5.98 lbs. of total evolved, it will beapparent that there is available a large water-carrying capacity in theheated flue gases for absorbing moisture from the mill juices which arebrought into direct and intimate contact with said gases in theapparatus as shown. It will, therefore, be seen that in addition to theheating of the sugar juicesby direct contact with the flue gases, thereresults the Very material advantage of a partial evaporation of thewater content of the juices, and a consequent concentration of thejuices, due first to the absorption by the hot flue gases of wateryvapors from juices up to or near saturation of the gases, and sec-- ond,the evaporation due to raising the juices to approximately the boilingpoint at or near the bottom of the apparatus by direct contact with thehottest portions of said flue gases, where the latter enter thecontainer 11.

6 A still further advantage of the process is the resultant economy infuel necessary to generate stea in the boilers. In actual ractice, it isf nd that the bagasse resultmg from the usual run of sugar cane does 10not provide suflicient fuel to generate steam to operate all of theapparatus of the sugar mill, so that it has been customary to provideadditional fuel in the form of wood or the like, which is fed to theboilers with bagasse, in order to generate adequate quan-. tities ofsteam. It has been demonstrated that the old type of juice heaterabsorbed substantially 23% of the steam necessary to operate the mill.The elimination of these juice heaters and the substitution of theapparatus for heating the juices by direct contact with the hot productsof combustion renders available for other purposes, the steam which washeretofore employed in operating the juice heaters. This means,obviously, that less steam will have to be developed, by at least 23%,which will bring the amount of steam required within the steamgenerating capacity of the bagasse supply ofthe mill, so that no extrafuel is necessary, but an actual surplus of bagasse results which may beemployed for other useful purposes.

It will also be apparent that inasmuch as a certain percentage ofmoisture is extract- 85 ed from the juices as the latter are subjectedto the hot products of combustion, the juices delivered to the quadrupleeffect evaporators will have already been concentrated or evaporated toa material degree, which will, therefore, result in a material saving inthe amount of steam required by said quadruple effect evaporators.

What I claim is v 1. The method of treatin sugar juices which comprisessubjecting t e same to direct contact with products of combustion from aboiler furnace or similar heat source.

2. The method of treating sugar juices which comprises subjecting thesame in 60 shower-like form to direct contact with products ofcombustion from a boiler-furnace or similar heat source.

3. The method of treating sugar juices which comprises showering saidjuices through a using current of flue gases from a steam boiler furnaceor the like.

In testimony whereof I aflix my signature.

ALFRED KRAFFT.

